<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    body{
      perspective: 500px;
    }
    .box{
      position: relative;
      height: 300px;
      width: 300px;
      margin: 200px auto;
      transition: all 1s;
      transform-style: preserve-3d;
    }
    .back,
    .front{
      position: absolute;
      width: 100%;
      height: 100%;
      top: 0;
      right: 0;
      border-radius: 50%;
      line-height: 300px;
      text-align: center;
      font-size: 20px;
      font-weight: 700;
      color: #FFFFFF;
    }
    .front{
      background-color: pink;

    }
    .back{
      background-color: purple;
      transform: rotateY(180deg);
    }
    .box:hover{
      transform: rotateY(180deg);
    }
  </style>
</head>
<body>
<div class="box">
  <div class="front">你好</div>
  <div class="back">傻逼</div>
</div>
</body>
</html>
